Marine mammal bycatch in southwest England: Taking a holistic approach to assess causes, impacts and evidence-based solutions

背景：ZSL的鲸目动物搁浅调查方案(CSIP)自1990年以来一直在运作，由Defra和下放的威尔士政府提供资金。它协调对英格兰和威尔士海岸线周围所有鲸鱼、海豚和江豚、海龟、海豹和大型体鲨的调查。除了记录每个搁浅的个体，他们还进行尸检以调查死亡原因，并更多地了解大型海洋脊椎动物在英国水域面临的威胁。自1990年成立以来，CSIP注意到，商业渔业意外诱捕海洋哺乳动物(兼捕)是每一年研究中一致的发现，是尸检检查的搁浅鲸目动物死亡的最大直接人为驱动因素(n=782,1990-2019年，英国搁浅数据集)。英格兰和威尔士的西南部，特别是康沃尔，是副渔获物相关死亡的热点地区。例如，在英国所有在验尸时被诊断为搁浅的普通海豚的兼捕案例中(1990年至2019年)，%的记录是在康沃尔记录的。2020年，在康沃尔搁浅的鲸目动物尸检中，约有三分之一被诊断为兼捕案例。该区域的兼捕很可能是由多个部门和多个船队推动的，对整个区域的物种以及英国专属经济区(EEZ)内外的物种产生影响。来自更广阔的北大西洋地区的海洋哺乳动物，包括普通的海豚、港口江豚和灰海豹，都知道在这一地区被误捕。因此，副渔获物是一个在区域、国家和国际各级影响海洋哺乳动物的国际问题。此外，当地离散的小型海洋哺乳动物种群(例如沿海/近岸宽吻海豚群落)将极易受到任何与副渔获物有关的死亡的影响。因此，兼捕也可能对一些物种/种群构成一个重大的保护问题。目前，关于该地区兼捕的主要驱动因素的信息相对有限，诸如物种分布和渔业之间的时空重叠以及使用的渔具类型等信息对于制定旨在管理威胁的政策至关重要。目的和方法：该项目将采取跨学科的方法，使我们了解西南水域海洋哺乳动物兼捕的情况。学生有机会根据他们的技能和兴趣制定项目的具体目标，但建议的目标包括：1)生态学/病理学：评估被认为对该地区鲸目动物有影响的渔具类型的现有证据基础。确定是否可以在调查搁浅期间收集额外的兼捕的法医证据，以帮助改进数据收集和诊断a。这名学生将与来自CSIP和更广泛的英国搁浅网络的搁浅科学家和兽医病理学家合作，设计一系列实验，以测试与不同类型的装备之间的相互作用如何出现在被兼捕的动物身上。评估兼捕、搁浅和其他辅助数据的现有来源，以综合更全面地了解不同海洋哺乳动物物种之间与兼捕有关的影响，包括时间和空间变化。2)海洋学：发展确定可能影响与兼捕有关的搁浅时空模式的潜在因素的方法a。通过在数值沿海海洋模式中进行反向粒子跟踪，从被捕获的动物搁浅的位置向后跟踪，以估计动物与渔具相互作用的潜在位置。使用若干数据来源(例如近岸船只监测数据和上岸信息)确定西南区域水域“高风险”捕捞活动的空间范围。3)政策分析：制定政策选择，以支持设计改进和潜在的解决方案

Background: The Cetacean Strandings Investigation Programme (CSIP) at ZSL has been running since 1990 and is funded by Defra and the Devolved Government of Wales. It coordinates the investigation of all whales, dolphins and porpoises, marine turtles, seals and large bodied sharks that strand around the English and Welsh coastline. As well as documenting each individual stranding, they conduct post-mortem examinations to investigate causes of death and learn more about the threats large marine vertebrates face in UK waters. Since its inception in 1990, CSIP have noted that accidental entrapment of marine mammals in commercial fisheries (bycatch) has been a consistent finding in every year of study and represents the largest direct anthropogenic driver of mortality in stranded cetaceans examined at necropsy (n=782, 1990-2019, data UK strandings dataset). The southwest of England and Wales, particularly Cornwall, is a hotspot for bycatch-related mortality. For example, 64% of all bycatch cases diagnosed in UK of stranded common dolphins examined at post-mortem examination (1990-2019) were recorded in Cornwall. During 2020, approximately one-third of post-mortem examinations of stranded cetaceans in Cornwall were diagnosed as bycatch cases.It is likely that bycatch in the region is driven by multiple sectors and multiple fleets impacting on species across the region; and inside/outside of the UK Exclusive Economic Zone (EEZ). Marine mammals from across the wider north Atlantic region, including common dolphins, harbour porpoises and grey seals, are known to succumb to bycatch in this area. Bycatch is therefore an international issue impacting marine mammals at regional, national and international levels. In addition, locally discrete and small marine mammal populations (e.g. coastal/inshore bottlenose dolphin communities) will be highly vulnerable to any bycatch-related mortality. Bycatch may therefore also pose a significant conservation issue for some species/populations.There is currently relatively limited information on the main drivers of bycatch in the area, and information such as the spatial and temporal overlap between species distributions and fisheries, and the types of gear used are essential for informing policies aimed at managing the threat.Aims and Approach: This project would take an interdisciplinary approach to informing our understanding of marine mammal bycatch in southwest waters. There is scope for the student to develop the specific objectives of the project depending on their skills and interests but suggested aims include;1) Ecology/Pathology: Assess the existing evidence base for gear types thought to impact on cetaceans in the region. Determine whether additional forensic evidence of bycatch could be gathered during investigation of strandings to help improve data collection and diagnosesa. The student would work with strandings scientists and veterinary pathologists from CSIP and the wider UK strandings network to design a series of experiments to test how interactions with different gear types may present in bycaught animals.b. Assess existing sources of bycatch, strandings and other ancillary data to synthesise a more holistic understanding of bycatch related impacts across different marine mammal species, including temporal and spatial variation.2) Oceanography: Develop methods for identifying potential factors that may influence the spatio-temporal patterns of bycatch-related strandingsa. By inverted particle tracking within a numerical coastal ocean model, backwards track bycaught animals from their stranding location to estimate the potential location for the animals interacting with fishing gearb. Identify the spatial extent of 'high risk' fishing activities in southwest regional waters using a number of data sources (e.g. Inshore Vessel Monitoring data and landings information).3) Policy analysis: Develop policy options to support design improvement and potential solutions